Lobby group agree to abandon Left (8)

I believe the answer is:

campaign

I'm a little stuck... Click here to teach me more about this clue!

'lobby' is the definition.
(I've seen this before)

I don't understand how the remainder of the clue works.

(Other definitions for campaign that I've seen before include "Crusase, drive" , "Electioneer" , "(E.g. military, political) project" , "offensive" , "In election period" .)

I've seen this clue in The Times and The Sunday Times.

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